Hookah water pipes have long been used in smoking combusted materials such as tobacco. As traditionally practiced, a hookah provides a water receptacle having an inlet conduit and at least one and often several outlet conduits. Smoke enters the water receptacle through the inlet conduit and is distributed to individual smokers through the outlet conduits, which are typically connected to hoses. Smoke is generated in a bowl in which a combustible substance such as tobacco is placed. A heat source is placed over the tobacco. In traditional practice, ignited charcoal is used as the heat source. The bowl is loaded with tobacco then covered in a small piece of perforated aluminum foil or a glass or metal screen. Lit coals are placed on top of the bowl containing tobacco. The hot air, heated by the charcoal ignites the tobacco, thus producing smoke vapor, which is passed down through the inlet conduit into the water receptacle.
Heating the tobacco generates smoke, which when one inhales through the outlet conduit, is drawn into the water receptacle through a supply conduit. The supply conduit is arranged to terminate below the level of the water within the water receptacle to assure filtration of raw smoke obtained from the bowl. The act of breathing air from the head space of the water receptacle induces partial vacuum in the head space, which in turn draws in smoke from the bowl through the supply conduit.
This arrangement requires that a fuel such as charcoal be provided and suitably ignited. This heat source must be maintained during smoking so that the combustible material is suitably ignited. With the use of lit charcoal, it is possible for products of combustion, such as volatile gasses and ash to be conducted into the water receptacle along with the smoke.
It is difficult at best to regulate the output of a combustion based heat source. The heat generated by ignited charcoal is not ideal because the heat generated is not constant or evenly distributed across the tobacco. Additionally the charcoal dissipates relatively quickly, requiring the addition of more charcoal to maintain proper combustion temperatures. Constant handling of ignited charcoal is an inconvenience to user and poses material risks of burn injury. Further, using ignited charcoal is not preferable as it will release unwanted carbon based compound into the smoke vapors, potentially fouling the flavor of the tobacco or releasing toxins that could cause harm the user. Such smoke and other products of combustion may be objectionable within a closed room or building.
Uses of electric heating sources have been proposed to overcome some of these limitations. U.S. Pat. No. 5,993,748 to Wheeler and U.S. Patent Appl. No. US2006/0086365 to Liu presents two such examples. Although an improvement over ignited combustible heat sources, there remain issues with electric heat sources for use with hookah type water pipes.
Heater construction material, air flow and distance of the heat source from the tobacco will directly impact the burn rate and vapor quality of tobacco when smoked in a hookah type water pipe. If the heat generated is too high or too close to the tobacco, the temperature will be too high and the ignition rate of the tobacco will be too fast, unnecessarily burning more tobacco than is desirable. If the heat generated is too low or the distance of the heat source too removed, the tobacco will not maintain ignition and the tobacco will be extinguished during idle periods. These considerations affect the smoke quality and the experience of the user.
The materials used for the construction of the heater are an important consideration. Many metals will react with air when heated, generating metal oxides or other compounds that can be harmful to the user. For example, when using copper as a material for an electric heater, copper (II) oxide can be generated by heating metallic copper in air. Copper (II) oxide is an irritant that can cause damage to the endocrine and central nervous system. Contact to the eyes or skin can cause irritation. Ingesting copper oxide is known to result in a continuous metallic taste, nausea, vomiting and stomach pain. Inhalation of fumes of cupric oxide can lead to damage to the lungs, septum and a disease called metal fume fever, which can result in flu like symptoms. Therefore a need exists to build an electric heater from materials that eliminate dissemination of toxins during use.
Different materials will also impact heat generation and heat transfer at the interface of the heat source and tobacco, which is critical to prevent unnecessary burning of tobacco both in terms of rate of burn during smoking and burn rate during idle periods of use. Control of heat output with electric heat sources is very difficult. Ideally, it is preferred to maintain the temperature below 800 degrees Fahrenheit. Above this temperature oxidation is common. Some substances have a high thermal conductivity and will readily transfer heat without distorting the form or shape of the heat transfer substance. Other materials have insulating properties that limit heat generation and heat transfer. Copper has a high thermal conductivity, but may have reactions with air that cause toxic vapors to be released. Therefore a need exist for an electric heater for used with hookah type water pipes that uses materials that adequately generate and transfer heat without reacting to release harmful vapors.
Air flow is also an important aspect to the proper burn of tobacco in a hookah type water pipe. Know electric heating systems do not control air flow and simply open air pathways that provide for free air flow rather than restricted or directed air as it is drawn into the bowl and flows across the heater. Free air flow tends to provide cooler air that in turn cools the interface between the heat source and tobacco. This requires higher temperature from the heater to maintain tobacco ignition. With higher temperatures and free air flow, tobacco is burned at a significantly faster rate when active and more energy is required to maintain the temperature. Therefore, a need exists for an electric heater with a managed air flow without increasing heat that optimized the burn rate of tobacco.
The distance between the heat source and the tobacco also impact the burn rate and quality of tobacco vapors. If a high temperature electric heater is placed at a significant distance from the tobacco it may still ignite the tobacco, but the heater may be at a temperature that may be dangerously hot and not suitable for the environment in which it is being used. Conversely, a lower temperature electric heater may be place directly on the tobacco to produce vapors. However, a low temperature heater would be inconvenient and require constant monitoring and reigniting of the tobacco. Additionally, an improperly distanced heater would inhibit proper air flow effecting the proper burn of the tobacco. Therefore a need exists for an electric heater for a hookah type water pipe that combines proper materials, air flow control and distance between the heat source and the tobacco to properly ignite tobacco.